Research outlined in this proposal is aimed at increasing our understanding of how the hormonal stimulus for oocyte maturation is controlled and transferred between cells within the ovarian follicle. Intercellular communication, via gap junctions, exist between oocytes and attached follicle cells within preovulatory ovarian follicles. The intracellular connections are interrupted during the course of hormone induced oocyte maturation under in vitro culture conditions. Our objective is to establish what role intercellular coupling, between somatic cells and oocytes, plays in controlling follicular steroidogenesis, hormone transfer and induction of maturation. To investigate these questions, the endogenous intrafollicular levels of progesterone will be monitored by radioimmunoassay following stimulation of steroidogenesis by pituitary hormones. We propose to measure steroid concentrations within the 2 compartments of the follicle (oocyte and follicle wall) at various stages of follicular differentiation in order to determine the correlation between hormone production, oocyte maturation and interruption of intercellular connections. Subsequently, we will determine whether hormone production and transfer (accumulation in the oocyte) can be dissociated following (1) experimental rupture of oocyte-follicle cell connections and (2) the use of known metabolic inhibitors which interfere with hormone induced maturation and interruption of cell-cell communication. Rupture of intercellular communication will be achieved with the use of specific hormone, cytoplasmic maturation promoting factor (MPF) or ion (calcium) deficient medium. To establish whether the oocyte influences follicle cell steroid production through intercellular connections, the physiological state of the oocyte will be varied by enucleation or microinjection with calcium ions or cAMP. Our results should provide definitive evidence concerning the role of intercellular coupling in mediating the transfer of a known hormone regulator of oocyte differentiation. Such information is crucial to understanding how cells communicate and how oocytes mature sufficiently to undergo fertilization and normal embryonic development.